Fig. 2: Microscopic structure and dynamic crossover of ad-molecules.
a–j Constant height AFM and simulated images of adsorbed monomer (a–e) and dimer (f–j) above the 2D bilayer ice. The images resolved at larger (a, b, f, g) and smaller (c, d, h, i) tip heights clearly show the monomer and dimer structures marked by green circles. The atomic configurations are presented in e, j. The O atoms of the 2D top- and bottom-layers are colored in red and blue, while ad-molecules and directly underlying molecules are yellow and purple. The H atoms are white. Top and side views are displayed in the upper and lower rows, respectively. Tip heights: 200 pm (a), 23.10 Å (b), 20 pm (c), 20.80 Å (d); 300 pm (f), 24.00 Å (g), 0 pm (h), 20.80 Å (i). All scale bars are 5 Å. k, l. Occurrence probability \({p}_{{{\rm{low}}}}\) (marked by blue line and squares) of underneath molecules below monomer (k) and dimer (l) configurations versus temperature from molecular dynamics (MD) simulations. Error bar represents six independent measurements. The vertical dashed line denotes the phase boundary between fractal (I & II) and compact (III) regimes. m. Arrhenius plot of the residence time τ (red circles in log scale with error bars) of ad-molecules as a function of annealing temperature in MD simulation. Error bar represents ten independent measurements. Vertical dashed lines denote dynamic crossovers consistent with the boundaries (I, II, III) identified in \({\bar{N}}_{{{\rm{nei}}}}\) vs. Tsim relation (black line and dots same as Fig. 1g). Linear fits serve as guides to the eye.
